Induced superconductivity in noncuprate layers of the Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta} high-temperature superconductor: Modeling of scanning tunneling spectra

We analyze how the coherence peaks observed in Scanning Tunneling Spectroscopy (STS) of cuprate high temperature superconductors are transferred from the cuprate layer to the oxide layers adjacent to the STS microscope tip. For this purpose, we have carried out a realistic multiband calculation for the superconducting state of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) assuming a short range d-wave pairing interaction confined to the nearest-neighbor Cu $d_{x^2-y^2}$ orbitals. The resulting anomalous matrix elements of the Green's function allow us to monitor how pairing is then induced not only within the cuprate bilayer but also within and across other layers and sites. The symmetry properties of the various anomalous matrix elements and the related selection rules are delineated.Comment: 9 pages, 2 figures. Accepted for publication in Phys. Rev.

Effect of orbital symmetry of the tip on Scanning Tunneling Spectra of Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta}

We discuss how variations in the scanning tunneling microscope (STM) tip, whether unintentional or intentional, can lead to changes in topographic images and dI/dV spectra. We consider the possibility of utilizing functionalized tips in order to improve the sensitivity of STM experiments to local irregularities at the surface or hidden below the surface layers. The change in the tip symmetry can radically alter the contrast of the topographic image due to changes in tip-surface overlap. The dI/dV curves change their shape according to which sample bands the tip orbital tends to overlap. In addition, relative phases between competing tunneling channels can be inverted by changing the tip symmetry, which could help reveal the origin of a local irregularity in tunneling spectrum.Comment: Accepted to Phys. Rev.

Spectral decomposition and matrix element effects in scanning tunneling spectroscopy of Bi2_2Sr2_2CaCu2_2O8+δ_{8+\delta}

We present a Green's function based framework for modeling the scanning tunneling spectrum from the normal as well as the superconducting state of complex materials where the nature of the tunneling process$-$ i.e. the effect of the tunneling 'matrix element', is properly taken into account. The formalism is applied to the case of optimally doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) high-Tc superconductor using a large tight-binding basis set of electron and hole orbitals. The results show clearly that the spectrum is modified strongly by the effects of the tunneling matrix element and that it is not a simple replica of the local density of states (LDOS) of the Cu-$d_{x^2-y^2}$ orbitals with other orbitals playing a key role in shaping the spectra. We show how the spectrum can be decomposed usefully in terms of tunneling 'channels' or paths through which the current flows from various orbitals in the system to the scanning tip. Such an analysis reveals symmetry forbidden and symmetry enhanced paths between the tip and the cuprate layers. Significant contributions arise from not only the CuO$_2$ layer closest to the tip, but also from the second CuO$_2$ layer. The spectrum also contains a longer range background reflecting the non-local nature of the underlying Bloch states. In the superconducting state, coherence peaks are found to be dominated by the anomalous components of Green's function.Comment: 16 pages, 10 figure

Hitsausprosessin robotisoinnin kannattavuuden arviointi

Tämän insinöörityön toimeksiantaja on Oy Haloila Ab. Oy Haloila Ab on maailman johtava käärintälaitteiden valmistaja. Insinöörityössäni keskityn kehittämään uuden putkirungon valmistusmenetelmää, ja arvioin olisiko valmistusmenetelmän automaatiotasoa kannattavaa kehittää. Työni tavoitteena on selvittää uuden tuotteen mahdollinen robottihitsauspotentiaali. Työni teoriapohja on suurelta osaa robotiikkaan ja piensarjatuotantoon perustuvaa. Piensarjatuotanto osiossa käsittelen joustavaa piensarjatuotantoa eli FM-järjestelmää. Robotiikan osalta teoreettinen pohja koostuu robottihitsauksesta, robottihitsauksen suunnittelusta, investointi-, kustannus-, ja vertailulaskelmista. Näiden laskelmien lisäksi käytin robottihitsauksen suunnittelun muistilistaa. Yksi tämän insinöörityön suurimmista osioista oli videoavusteinen valmistusmenetelmä analyysi. Yhdistin analyysiin suunnittelu- ja tuotantohenkilöstön haastatteluja, jotka kokosin yhdeksi paketiksi. Tulevaisuuden investointien pohjaksi laskin myös investointilaskelman ja robotin ja ihmisen kustannusvertailulaskelman. Työmenetelmien kehittämistä varten tein myös robottihitsauksen suunnittelun muistilistan, jossa perehdyin putkirungon tämän hetkiseen valmistusmenetelmään, ja pohdin olisiko putkirungon hitsaaminen tulevaisuudessa robotisoidusti kannattavaa. Videoavusteisen valmistusmenetelmä analyysin tuloksena löytyi kehittämispotentiaalia koskien hitsaus ja kokoonpano työvaiheita. Muistilistan tuloksina sain työ-, ja hitsausvaiheita, jotka sopisivat robotisoitaviksi ja työmenetelmään ideoita robotisoinnin toteuttamiseksi. Vertailu-, ja investointilaskelmien tuloksista sain suuntaa antavaa tietoa siitä, miten käsinhitsaus olisi korvattavissa robotilla, miten paljon robottia tulisi vuotuisesti kuormittamaan ja millainen takaisinmaksuaika investoinnilla olisi tietyillä raja-arvoilla. Toivon näiden tulosten antavan apua työmenetelmien kehittämiseen ja päätöksentekoon robotti-investointeja tehtäessä.The commissioner for this Bachelor's thesis is Haloila corporation. Haloila corporation is the world's leading manufacturer of automatic pallet load wrapping machines. This thesis concentrates on developing the production method of pipe frames and estimating profitability to develop the automation level of the production procedure. The priority is to examine the possible robot welding potential of the new product. The theory part discusses mainly short-run production and robotics. In the short-run production part flexible manufacturing or FMS is presented. Concerning robotics theory robot welding, designing robot welding, investment-, expenses-, and comparison calculations are discussed. In addition to these calculations, a check list was used concerning the design of robot welding. The largest part of the thesis work was a video-aided production procedure analysis. The analysis combines the interviews of design and production personnel gathered in to a unified entity. For future investments calculations on investment and a human versus robot expenses comparison were completed. For the development of production procedures a check list was drafted to become familiar with the current production procedure of pipe frames and consider the profitability of robot welding the pipe frame in the future. As a result of the video-aided production procedure analysis development potential was found concerning both welding and assembly stages. As a result of the check list the work and welding stages were determined which would be appropriate to be robotized and ideas were developed for executing the robotizing. The results of the comparison and investment calculations were suggestive about the way hand welding could be replaced by robot welding, the robot's annual work load and the payback time of the investment with certain boundaries. These results should help developing the production procedures and decision making when planning robot investments

Retrospective Analysis of Artifacts in Cone Beam Computed Tomography Images Used to Diagnose Chronic Rhinosinusitis

Background: Cone beam computed tomography (CBCT) is frequently used to corroborate the signs and symptoms of chronic rhinosinusitis (CRS). However, artifacts induced by dental restorations might complicate the diagnosis of CRS. Here, we assessed the frequency and location of artifacts in CBCT images taken to confirm the CRS. Methods: All CBCT images of the patients referred to the Emergency Radiology unit, Turku University Hospital, with an indication of CRS in 2017 were re-examined. The prevalence of the artifacts was analyzed in three cross-sectional views and three horizontal levels delimited by anatomical landmarks. Results: In total, 214 CBCT images of patients with CRS were evaluated. The diagnosis of apical periodontitis (AP) was impaired by artifacts present in 150/214 images (70%). The diagnosis of CRS was impaired in 5 of the 214 images (2.3%). The main origins of the artifacts were large dental fillings or crowns, and endodontic fillings were present in 95% (203/214) and 52% (111/214) of the images, respectively. Conclusions: AP as an etiology of CRS is possible to miss because of artifacts originating from dental and endodontic fillings in the CBCT images of the paranasal sinuses